The present invention relates to automatic electronic or "computer" flash systems. In particular, the present invention relates to a correct exposure annunciator for use with automatic electronic flash systems.
Automatic electronic flash systems include a light producing means, generally a flash tube, which is actuated to illuminate a scene which is being photographed. A light sensing or exposure control circuit detects the scene illumination and actuates a light teminating or light quenching means when sufficient light has been produced to properly expose a light sensitive film of an associated camera.
There is a need for an annunciator which will indicate to the photographer whether sufficient light has been produced to properly expose the film. When an automatic electronic flash system is used, the exposure control circuit will terminate the light flash prior to its normal conclusion if sufficient light has been received. In U.S. Pat. No. 3,706,911 by Dennis J. Wilwerding, a correct exposure annunciator circuit is provided. In this circuit, a switch is responsive to the operation of the light quenching means. The closure of this switch energizes the annunciator.
Although the correct exposure annunciator circuit of the Wilwerding patent is generally satisfactory, it does have some shortcomings. In particular, it typically requires a relatively large number of additional components (12 to 15 components in many cases). This increases cost and affects reliability of the flash system.